Since the retention of cationic nutrient elements such as nitrogen and potassium is weak in volcanic ash soils, these nutrients are easily eluviated from the soils. On the other hand, the volcanic ash soils strongly fix phosphorus and efficiency of phosphorus fertilizers is low. Thus, volcanic ash soils are heavily fertilized in usual. However, this high input meaagement is not good for inland water system. Improvement of this high input management is strongly desired from the viewpoint of environmental protection and savings of fertilizer resources. We tried to improve this high input management using Co-situs application of polyolefin-coated (POC) fertilizers.The Co-situs application of total amount of POC fertilizers needed for one cropping season with corn seeds were very effective in improving high-input management and in reducing labor for fertilizer application. There was no fertilizer burning of corn roots since the nutrients in the POC fertilizers are slowly released in harmony with corn growth. Root development was not so affected by the Co-situs application of POC fertilizers. Thus, naturally supplied nutrients and water in soils are normally absorbed by plants as usual. The corn yield of the Co-situs application plot was almost the same with conventional management plot. The efficiency of POC nitrogen fertilizer was not so much affected by weather since the release of nutrients from the POC fertilizers is dependent on only soil temperature.